At present, no satisfactory therapy exists for severe manifestations of SLE except for renal disease. Even renal disease does not respond well to conventional therapy when the creatinine clearance is markedly reduced. In this study we will test the efficacy of high dose intravenous therapy with cyclophosphamide for the control of severe SLE unresponsive to a trial of high doses of prednisone (up to 2 mg per kg for 3 weeks).